OpenTelemetry Environment Variable Specification
The goal of this specification is to unify the environment variable names between different OpenTelemetry SDK implementations. SDKs MAY choose to allow configuration via the environment variables in this specification, but are not required to. If they do, they SHOULD use the names listed in this document.
Special configuration types
Numeric value
If an SDK chooses to support an integer-valued environment variable, it SHOULD support nonnegative values between 0 and 2³¹ − 1 (inclusive). Individual SDKs MAY choose to support a larger range of values.
Enum value
For variables which accept a known value out of a set, i.e., an enum value, SDK implementations MAY support additional values not listed here. For variables accepting an enum value, if the user provides a value the SDK does not recognize, the SDK MUST generate a warning and gracefully ignore the setting.
Duration
Any value that represents a duration, for example a timeout, MUST be an integer representing a number of milliseconds. The value is non-negative - if a negative value is provided, the SDK MUST generate a warning, gracefully ignore the setting and use the default value if it is defined.
For example, the value 12000 indicates 12000 milliseconds, i.e., 12 seconds.
General SDK Configuration
| Name | Description | Default | Notes |
|---|---|---|---|
| OTEL_RESOURCE_ATTRIBUTES | Key-value pairs to be used as resource attributes | See Resource SDK for more details. | |
| OTEL_LOG_LEVEL | Log level used by the SDK logger | "info" | |
| OTEL_PROPAGATORS | Propagators to be used as a comma separated list | "tracecontext,baggage" | Values MUST be deduplicated in order to register a Propagator only once. |
| OTEL_TRACES_SAMPLER | Sampler to be used for traces | "parentbased_always_on" | See Sampling |
| OTEL_TRACES_SAMPLER_ARG | String value to be used as the sampler argument | The specified value will only be used if OTEL_TRACES_SAMPLER is set. Each Sampler type defines its own expected input, if any. Invalid or unrecognized input MUST be logged and MUST be otherwise ignored, i.e. the SDK MUST behave as if OTEL_TRACES_SAMPLER_ARG is not set. |
Known values for OTEL_PROPAGATORS are:
-
"tracecontext": W3C Trace Context -
"baggage": W3C Baggage -
"b3": B3 Single -
"b3multi": B3 Multi -
"jaeger": Jaeger -
"xray": AWS X-Ray (third party) -
"ottracer": Lightstep (third party) -
"ottrace": OT Trace (third party)
Known values for OTEL_TRACES_SAMPLER are:
-
"always_on":AlwaysOnSampler -
"always_off":AlwaysOffSampler -
"traceidratio":TraceIdRatioBased -
"parentbased_always_on":ParentBased(root=AlwaysOnSampler) -
"parentbased_always_off":ParentBased(root=AlwaysOffSampler) -
"parentbased_traceidratio":ParentBased(root=TraceIdRatioBased)
Depending on the value of OTEL_TRACES_SAMPLER, OTEL_TRACES_SAMPLER_ARG may be set as follows:
- For
traceidratioandparentbased_traceidratiosamplers: Sampling probability, a number in the [0..1] range, e.g. "0.25". Default is 1.0 if unset.
Batch Span Processor
| Name | Description | Default | Notes |
|---|---|---|---|
| OTEL_BSP_SCHEDULE_DELAY | Delay interval between two consecutive exports | 5000 | |
| OTEL_BSP_EXPORT_TIMEOUT | Maximum allowed time to export data | 30000 | |
| OTEL_BSP_MAX_QUEUE_SIZE | Maximum queue size | 2048 | |
| OTEL_BSP_MAX_EXPORT_BATCH_SIZE | Maximum batch size | 512 | Must be less than or equal to OTEL_BSP_MAX_QUEUE_SIZE |
Span Collection Limits
| Name | Description | Default | Notes |
|---|---|---|---|
| OTEL_SPAN_ATTRIBUTE_COUNT_LIMIT | Maximum allowed span attribute count | 1000 | |
| OTEL_SPAN_EVENT_COUNT_LIMIT | Maximum allowed span event count | 1000 | |
| OTEL_SPAN_LINK_COUNT_LIMIT | Maximum allowed span link count | 1000 |
OTLP Exporter
See OpenTelemetry Protocol Exporter Configuration Options.
Jaeger Exporter
| Name | Description | Default |
|---|---|---|
| OTEL_EXPORTER_JAEGER_AGENT_HOST | Hostname for the Jaeger agent | "localhost" |
| OTEL_EXPORTER_JAEGER_AGENT_PORT | Port for the Jaeger agent | 6832 |
| OTEL_EXPORTER_JAEGER_ENDPOINT | HTTP endpoint for Jaeger traces | "http://localhost:14250" |
| OTEL_EXPORTER_JAEGER_USER | Username to be used for HTTP basic authentication | - |
| OTEL_EXPORTER_JAEGER_PASSWORD | Password to be used for HTTP basic authentication | - |
Zipkin Exporter
| Name | Description | Default |
|---|---|---|
| OTEL_EXPORTER_ZIPKIN_ENDPOINT | Endpoint for Zipkin traces | "http://localhost:9411/api/v2/spans" |
Addtionally, the following environment variables are reserved for future usage in Zipkin Exporter configuration:
OTEL_EXPORTER_ZIPKIN_PROTOCOL
This will be used to specify whether or not the exporter uses v1 or v2, json, thrift or protobuf. As of 1.0 of the specification, there is no specified default, or configuration via environment variables.
Prometheus Exporter
| Name | Description | Default |
|---|---|---|
| OTEL_EXPORTER_PROMETHEUS_HOST | Host used by the Prometheus exporter | All addresses: "0.0.0.0" |
| OTEL_EXPORTER_PROMETHEUS_PORT | Port used by the Prometheus exporter | 9464 |
Exporter Selection
We define environment variables for setting a single exporter per signal.
| Name | Description | Default |
|---|---|---|
| OTEL_TRACES_EXPORTER | Trace exporter to be used | "otlp" |
| OTEL_METRICS_EXPORTER | Metrics exporter to be used | "otlp" |
Known values for OTEL_TRACES_EXPORTER are:
-
"otlp": OTLP -
"jaeger": Jaeger gRPC -
"zipkin": Zipkin (Defaults to protobuf format)
Known values for OTEL_METRICS_EXPORTER are:
-
"otlp": OTLP -
"prometheus": Prometheus
Language Specific Environment Variables
To ensure consistent naming across projects, this specification recommends that language specific environment variables are formed using the following convention:
OTEL_{LANGUAGE}_{FEATURE}
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